The wet and dry particle depositions, particle and gaseous phase PAHs in atmosphere, and dissolved phas? PAHs in water were sampled by passive sampler, high-volume air sampler and semipeameiable membrane device (SPMD) in Lake Luhu, respectively. According to the stagnant two-film model and Henry theory, the direction and magnitude of fluxes of PAHs across the air-water interface in Luhu Lake were calculated based on the analytical data. The result showed that the atmosphere deposited about 1300 g of PAHs to water and water volatilized about 220 g of PAHs to atmosphere. PAHs with different molecular weights have different predominant processes across the lake water-air interface